A solar photovoltaic (PV) array is a parallel arrangement of strings of series-connected PV panels. A string in the context of PV arrays is an arrangement of PV panels connected together in series. A PV array is composed of multiple strings of PV panels. Each string output is received in a device called a combiner, which “combines” the current from each string into a larger conductor, called a busbar, for feeding downstream equipment such as disconnect switches, possibly other lower-level combiners, and ultimately to a DC-to-AC inverter that converts the DC currents produced by each string of the PV array into a corresponding AC current. The combiner can receive strings from one or more PV arrays.
In the combiner, which typically takes the form of an enclosure, circuit breakers or fuses are used to limit backfeeding current from one or more strings into another. Backfeeding current into a PV panel can damage the wiring panel or otherwise adversely affect the performance of the PV array.
Individual strings connected to the combiner can underperform for one of several reasons, including the presence of a ground fault in the string, a loose wire in the string, solar tracking of the PV panel is misadjusted, and so forth. As will be appreciated solar PV arrays can occupy extensive surface areas. A typical PV system might contain multiple PV arrays and dozens or even hundreds of PV panels.
Conventional software in the DC-to-AC inverter can indicate a drop in performance of the PV array as a whole, but the inverter has no way of knowing which PV array is underperforming or has a problem let alone which individual string is underperforming or has a problem. To troubleshoot which individual string might be the source of the problem involves manual labor and extensive troubleshooting of the entire array until the source of the problem is found. If an underperforming or troublesome string goes unnoticed, is ignored, or is undetected, a substantial decrease in power generation and a loss of revenue can occur. More seriously, if the problem is caused by a loose wire connection or a ground fault, a hazardous condition can persist creating a potentially dangerous condition depending on the installation of the string, such as on a building or in other areas where humans can be present.